Well we don't know for sure when the new cards will be coming out, their price range or possible performance. Do you need the upgrade desperately? Go for a 1080ti. Can you wait for an indefinite amount of time? Wait.
Also the 80Ti version historically doesn’t come out for 9-12 months after the non Ti 80 card so if you were thinking about the 1180Ti we may have another year before that launches.